Intermediate for composite materials

ABSTRACT

An intermediate for a composite material is disclosed. The intermediate is obtained by impregnating an epoxy resin composition containing a specific additive into a carbon fiber. The composite material obtained from the intermediate has improved mechanical properties.

This is a continuation-in-part of application Ser. No. 763,180, filedAug. 7, 1985, now abandoned.

FIELD OF THE INVENTION

This invention relates to an intermediate for a composite materialhaving excellent mechanical properties.

BACKGROUND OF THE INVENTION

Various resin compositions have conventionally been used as matrices forcomposite materials. In the particular field of thermosetting resins,epoxy resins have widely been used as matrix resins because of theirexcellent mechanical properties, such as strength, elongation, heatresistance, etc., but when reinforcing materials are used compositematerials containing reinforcing materials become more or lessstrengthened and, generally, the strength of reinforcing material isreflected in or transferred to the composite material. However, even inthe case of using epoxy resins, the degree of strengthening or transferdue to the reinforcing materials is still unsatisfactory particularly interms of compression characteristics and, therefore, improvement in thisrespect has been demanded. An attempt to this effect was directed to anincrease in rigidity of resins per se, but generally an increase inrigidity is accompanied with an unfavorable increase in heat resistance,resulting in a significant reduction in elongation. Such resins connotbe used in some applications because of their brittleness. It wasproposed in The British Polymer Journal, 15, 66 (March, 1983) that areaction product between an epoxy compound ##STR1## and an amidecompound ##STR2## is added to a system comprising an epoxy resin and ahardener to thereby improve the physical properties of resins, but noconsideration is given to the improvement of the compressioncharacteristics of the composites when they are used as a matrix resinfor composite materials. In connection to the above proposal, there havealso been proposed a reaction product between an epoxy compound and anamine compound in EP-A-103392 and a reaction product between an epoxycompound and an amide compound in EP-A-103968, but neither contains anysuggestion of these materials for use as a matrix resin for compositematerials.

SUMMARY OF THE INVENTION

In the light of these circumstances, the present inventors haveconducted extensive studies on intermediate for composite materialswhich can provide excellent mechanical properties, particularlycompression characteristics. As a result, they discovered an additivewhich can remarkably improve the rigidity of cured epoxy resins withoutimpairing their elongation and confirmed that an epoxy resin compositioncomprising an epoxy resin, a hardener, a hardening accelerator and theabove-described additive when used as a matrix gives pronouncedlyimproved composite mechanical properties.

The present invention relates to an intermediate for a compositematerial, which is obtained by impregnating a reinforcing material withan epoxy resin composition containing, as an additive, at least one ofcompounds represented by the following formulae (I) ##STR3## wherein R₁,R₂ which may be the same or different, each represents a propyl group, abutyl group, etc), a substituted or unsubstituted, saturated alicyclicgroup having 5 to 17 carbon atoms (e.g., a cyclopentyl group, acyclohexyl group, a 2-ethylcyclohexyl group, etc.), a substituted orunsubstituted aromatic group having 6 to 17 carbons atoms (e.g., aphenyl group, a tolyl group, etc.), or a substituted or unsubstituted,saturated or unsaturated 5- or 6-membered heterocyclic group containingN, O or S as hetero atom ##STR4## or a group of formula ##STR5## whereinR₅ and R₆, which may be the same or different, each represents ahydrogen atom or a substituted or unsubstituted, saturated aliphaticgroup having 1 to 17 carbon atoms (e.g., a methyl group, an ethyl group,an ethyl hexyl group, etc.), a substituted or unsubstituted, saturatedalicyclic group having 5 to 17 carbon atoms (e.g., a cyclopentyl group,a cyclohexyl group, a 2-ethylhexyl group, etc.), a substituted orunsubstituted aromatic group having 6 to 17 carbon atoms (e.g., a phenylgroup, a tolyl group, etc.), or a substituted or unsubstituted,saturated or unsaturated 5- or 6-membered heterocyclic group containingN, O or S as hetero atom ##STR6## wherein said substituted aliphatic,alicyclic, aromatic and heterocyclic groups may contain as a substituenta halogen atom (e.g., chlorine, bromine, etc.), an alkoxy group having 1to 3 carbon atoms (e.g., a glycidyloxy group, a methoxy group, an ethoxygroup, etc.), an aryloxy group having 6 to 17 carbon atoms (e.g., aphenoxy group, etc.), an acyl group having 2 to 7 carbon atoms (e.g., anacetyl group, a benzoyl group, etc.); R₃ and R₄, which may be the sameor different, each has the same meanings as defined for R₁ and R₂, or agroup of formula R--OCH₂ -- wherein R has the same meaning as definedfor R₁ and R₂ ##STR7## and X represents an oxygen atom, a sulfur atom orN--R₇ wherein R₇ represents a hydrogen atom or has the same meaning asdefined for R₁ and R₂.

DETAILED DESCRIPTION OF THE INVENTION

Among the compounds represented by the formulae (I), this having a bulkyand highly rigid substituent, such as an aromatic group, a heterocyclicgroup and an alicyclic group, in the molecule thereof are particularlyeffective.

Specific examples of the compounds which can preferably be used in thepresent invention are shown below: ##STR8##

The compounds represented by the formula (I) can be obtained, forexample, through reactions between epoxy compounds and the correspondingamine compounds, amide compounds and urea compounds, respectively, asshown in the following reaction schemes: ##STR9## wherein R₁ to R₄ and Xare as defined above.

The epoxy compounds represented by the formula (IV) which can be used inthe preparation of the compounds of the present invention include lowmolecular epoxy compounds, such as epichlorohydrin, phenylglycidylether, ethylene oxide, propylene oxide, butadiene oxide, dimethylpentanedioxide, diglycidyl ether, butanediol diglycidyl ether, ethylene glycoldiglycidyl ether, vinylcyclohexene dioxide, limonene dioxide,bis(2,3-epoxycyclopentene) ether, divinylbenzene dioxide, resorcindiglycidyl ether, 2-glycidyl phenylglycidyl ether,3,4-epoxy-6-methyl-cyclohexylmethyl-3,4-epoxymethylcyclohexenecarboxylate,butylglycidyl ether, styrene oxide, p-butylphenol glycidyl ether,cresylglycidyl ether, glycidyl methacrylate, allylglycidyl ether,cyclohexanevinyl monoxide, dipentene monoxide, α-pinene oxide,3(pentadecyl) phenylglycidyl ether, etc.

The compounds represented by the formula (V) which can be used in theabove-described reaction (A) include alicyclic amines, e.g.,cyclohexylamine, dicyclohexylamine, etc.; aromatic amines, e.g.,aniline, p-aminobenzoic acid, 3,4-xylidine, m-xylylenediamine,diaminodiphenyl ether, dibenzylamine, benzylamine, etc.; heterocyclicamines, e.g., 4-aminopyridine, N-aminopropylmorpholine,bisaminopropylpiperazine, etc., heterocyclic compounds, e.g.,piperazine, 2-pipecoline, piperidine, pyrrolidine, 5-fluorouracil,N-methylpiperazine, etc.; and amino acids, e.g., β-alanine,glycylglycine, glutamic acid, γ-aminobutyric acid, γ-aminocaproic acid,glycine, etc.; acid amides, e.g., 4-hydroxyphenylamide,4-hydroxyphenylacetamide, phenylacetoacetamide, etc., or correspondingmonothio- or dithiocarboxylic acids thereof; acetoguanamine; 3-amino-1,2,4-triazole isocyanuric acid; imidiazoles, e.g., 2-methylimidazole,2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole,2-heptadecylimidazole,2,4-diamino-6-[2'-methylimidazolyl-(1)']-ethyl-s-triazine,2,4-diamino-6-[2'-ethyl-4-methylimidazolyl-(1)']-ethyl-s-triazine,2-phenyl-4-methyl-5-hydroxymethylimidazole,2-phenyl-4,5-dihydroxymethylimidazole, a 2-methylimidazole-isocyanuricacid adduct, a 2-phenylimidazole-isocyanuric acid adduct, etc.;5,5-dimethylhydantoin; benzoguanamine; 1-methylol-5,5-dimethylhydantoin,melamine; 1,3-diphenylguanidine; di-o-tolylguanidine;1-o-tolylbiguanide, and the like; single or mixed asymmetrical urea orthiourea compounds derived from ammonia; aliphatic amines, e.g.,methylamine, ethylamine, n-propylamine, n-butylamine, isopropylamine,2-ethylhexyloxypropylamine, 3-ethoxypropylamine, di-2-ethylhexylamine,dibutylaminopropylamine, diisobutylamine, 3-methoxypropylamine,allylamine, secbutylamine, isopropanolamine, 2-ethylhexylamine,ethylenediamine, hexamethylenediamine, etc.; alicyclic amines, e.g.,cyclohexylamine, dicyclohexylamine, etc.; aromatic amines, e.g.,aniline, p-aminobenzoic acid, 3,4-xylidine, dibenzylamine, benzylamine,etc.; heterocyclic amines, e.g., 4-aminopyridine,N-aminopropylmorpholine, 1-amino-1 -methylpiperazine,bisaminopropylpiperazine, etc., heterocyclic compounds, e.g.,piperazine, 2-pipercoline, piperidine, pyrrolidine, 5-fluorouracil,morpholine, N-methylpiperazine, etc.; and amino acids, e.g., β-alanine,glycylglycine, glutamic acid, γ-aminobutyric acid, γ-aminocaproic acid,glycine, etc.; acetoguanamine, 3-amino-1,2,4-triazole, osocyanuric acid,imidazoles, e.g.,2,4-diamino-6-[2'-methylimidazolyl-(1)']ethyl-s-triazine,2,4-diamino-6-[2'-undecylimidazolyl-(1)']ethyl-s-triazine,2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1)']-ethyl-s-triazine, a2-methylimidazole-isocyanuric acid adduct, a2-phenylimidazole-isocyanuric acid adduct. etc., 5,5-dimethylhydantoin,benzoguanamine, 1-methylol-5,5-dimethylhydantoin, melamine,1,3-diphenylguanidine, di-o-tolylguanidine, 1-o-tolybiguanide,N,N'-diphenylthiourea, 2-mercapto-2-imidazoline, N,N'-diethylthiourea,N,N'-dibutylthiourea, N,N'-diluarylkthiourea, and the like.

The reaction (A) can be carried out in the presence or absence of anorganic solvent at a temperature of from room temperature to 180° C.while stirring for 0.5 to 10 hours. The solvent to be used includearomatic hydrocarbons, e.g., benzene, toluene, etc.; aliphatichydrocarbons, e.g., hexane, ligroin, etc.; halogenated hydrocarbons,e.g., carbon tetrachloride, chloroform, etc.; and ethers, e.g., dioxane,tetrahydrofuran, etc. In carrying out the reaction the chemicalequivalent ratio of epoxy group to an NH bond ranges from 1/10 to 10/1,and preferably from 1/1.5 to 1.5/1. (cf. Henry Lee and Kris Neville;Handbook of Expoxy Resins", S.5-12 and 5-13 McGraw-Hill Book Co., 1967))

SYNTHESIS EXAMPLE 1 Synthesis of Compound B-3

In a flask equipped with a condenser, a dropping funnel and a stirrer,there was placed 168 g of vinylcyclohexene dioxide and heated at 170° C.while stirring. Aniline (93 g) contained in the dropping funnel wasadded portionwise at a rate of 2 g/min. After completion of addition,the mixture was allowed to react for 1 hour to obtain a composition.Formation of Compound B-3 was confirmed by NMR spectral analysis.

SYNTHESIS EXAMPLE 2 Synthesis of Compound B-7

4-Hydroxyphenylacetamide (150 g) was dissolved in 160 g of phenylglycidyl ether and the solution was stirred for 5 hours at 90° C. toobtain a viscous liquid composition. Formation of Compound B-7 wasconfirmed by NMR spectral analysis.

The epoxy resin composition for intermediate for composite materialsaccording to the present invention usually comprises from 2 to 150 partsby weight, and preferably from 10 to 50 parts by weight, of theabove-described additive per 100 parts by weight of the total amount ofthe resin composition (an epoxy resin, a hardener and/or a hardeningaccelerator). If the amount of the additive is less than 2 parts byweight, a substantial effect cannot be exerted. Amounts exceeding 150parts by weight seriously reduce heat-resistance.

The epoxy resin to be used in the epoxy resin composition includeswell-known epoxy resins, such as polyglycidyl ethers ofdiphenylolalkanes, e.g., diphenylolpropane, diphenylolethane,diphenylolmethane, etc.; polyhydric phenol polyglycidyl ethers, e.g.,novolak, resol, etc.; epoxy resins produced by epoxidation of alicycliccompounds (e.g., cyclohexane, cyclopentadiene, dicyclopentadiene,(etc.), e.g., an ester of 3,4-epoxy-6-methylcyclohexanecarboxylic acidand methyl 3,4-epoxy-6-methylcyclohexanoate; poly(epoxyalkyl) ethers ofaliphatic polyoxy compounds, e.g., ethylene glycol, glycerin, etc.;epoxyalkyl esters of carboxylic acids, e.g., glycidyl esters of aromaticor aliphatic carboxylic acids; and the like. These epoxy resins may beused alone or in combination thereof.

A preliminary condensate between the above-enumerated epoxy resin and ahardener may also be employed as epoxy resin of the epoxy resincomposition.

The preliminary condensate which can be used in the present inventioncan be prepared by subjecting at least one polyamine or acidic substancehaving a polycarboxylic group, a polycarboxylic acid anhydride group ora mixed group thereof and the above-mentioned epoxy resin to heattreatment to increase the viscosity of the mixture at least 3 timeswithout inducing gelation.

Examples of the polyamine to be used for obtaining the preliminarycondensate are aromatic polyamines, e.g., o-phenylenediamine,m-phenylenediamine, 4,4'-methylenedianiline,4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone,m-xylylenediamine, etc.; and aliphatic polyamines, e.g.,triethylenetetramine, diethylenetriamine, isophoronediamine,1,3-diaminocyclohexane, menthanediamine, cyanoethylateddiethylenetriamine, N-aminoethylpiperazine, methyliminobispropylamine,aminoethylethanolamine, polyethylenediamine, polymethylenediamine, etc.These polyamines can be used alone or in combination thereof.

Examples of the acidic substance which can be used as a hardener forobtaining the preliminary condensate are phthalic anhydride, succinicanhydride, maleic anhydride, hexahydrophthalic anhydride, pyromelliticanhydride, benzophenonetetracarboxylic anhydride, trimellitic anhydride,itaconic anhydride, citraconic anhydride, dodecenylsuccinic anhydride,chlorendic anhydride, methylcyclopentadiene-maleic acid adduct,methyltetrahydrophthalic anhydride, maleic anhydride-linoleic acidadduct, cyclopentanetetracarboxylic anhydride, alkylatedendalkylenetetrahydrophthalic anhydrides, ethylene glycolbistrimellitate, glycerin tristrimellitate, and the like. These acidicsubstances may be used alone or in combination of two or more thereof.

The chemical equivalent ratio of the polyamine or acidic substance tothe epoxy resin is important and ranges from 1:1 to 1:6, preferably from1:1.4 to 1:6, and more preferably from 1:1.5 to 1:5. If this equivalentratio is more than 1:1, the excess polyamine or acidic substance reducesheat resistance, strength and the like of a hardened product. On theother hand, if it is less than 1:6 the polyamine or acidic substancebecomes short to deteriorate heat resistance or strength of a hardenedproduct. The term "chemical equivalent ratio" as herein used means thatone epoxy group is equivalent to one N--H bond or carboxylic acid groupor one half carboxylic acid anhydride group.

The temperature for the heat treatment for obtaining the preliminarycondensate is determined depending on the time required for reaching adesired viscosity and controllability of viscosity. When the epoxy resinis used in a large excess within the above-described range, it ispossible to shorten the treating time by raising the heatingtemperature. On the other hand, when the epoxy resin is used in a slightexcess, the reaction mixture is readily gelled so that the heatingtemperature should be controlled lower. In general, the heatingtemperature ranges from 50° to 200° C., and preferably from 120° to 170°C.

The condensation reaction is usually carried out under normal pressure,but may be effected under pressure. The reaction is usually conducted inthe absence of a solvent, but when any one or more of the epoxy resins,polyamines and acidic substances are solid at room temperature, solventmay be employed. Such being the case, hydrocarbons that do not adverselyaffect the produced preliminary condensate, such as xylene, toluene,cyclohexane, etc., are preferred. In the case where a solvent isemployed, the resulting reaction mixture containing the solvent may beused as such depending upon the application of the product. Ifnecessary, the solvent may be removed from the reaction mixture bydistillation under reduced pressure or a like technique.

The reaction is stopped at the point when the viscosity of the reactionmixture is increased to at least three times the initial one. The upperlimit of the viscosity is not particularly restricted as long asgelation does not occur, but the reached viscosity is usually from 10 to100 times the initial one. The term "viscosity" as herein used means aviscosity as determined by a Brookfield viscometer. The stopping of thereaction can be effected by a known method appropriately selectedaccording to the purpose, for example, a method of quenching thereaction mixture to room temperature, a method of adding a solvent inertto an epoxy group, e.g., acetone, methyl ethyl ketone, toluene, xylene,etc., a method of spreading the reaction mixture in thin film over acooled plate, and the like.

Use of the above-described preliminary condensate in the epoxy resincomposition of the present invention has the following advantages. Thoseprepared from polyamines and epoxy resins improve working stability(working life) of the composition and also alleviate toxicity andmoisture-absorbing property of polyamines as compared with a mere blendof the polyamines (hardener) and epoxy resins. Those prepared from theacidic substances and epoxy resins achieve reduction in a hardeningtemperature and a hardening time as compared with a mere blend of theacidic substances (hardener) and epoxy resins. Further, thesepreliminary condensates also have an advantage of possible reduction ofa rate of contraction upon hardening.

The hardener which can be added to the epoxy resin composition accordingto the present invention includes polyamines, such as those enumeratedabove with respect to the preliminary condensates; acidic substances,such as those enumerated above with respect to the preliminarycondensates; and, in addition, acid hydrazides, such as isophthalic acidhydrazide, adipic acid hydrazide, sebacic acid hydrazide, etc.;polyamideamines; dicyandiamide; 1-o-tolylbiguanide; ketimine; and thelike. Of these, dicyandiamide is particularly preferred in view ofsufficient preservability and working stability of the resulting epoxyresin composition.

The hardening accelerator which can be added to the epoxy resincomposition in accordance with the present invention include borontrifluoride complexes, e.g., a boron trifluoride monoethylamine complexcompound, a boron trifluoride piperidine complex compound, etc.;imidazole compounds, e.g., 2-methylimidazole, 2-ethyl-4-methylimidazole,etc.; triphenyl phosphite; butanetetracarboxylic acid;1,8-diazabicyclo(5.4.0)undecene-7; and urea compounds represented by theformula (VIII): ##STR10## wherein Y and Z, which may be the same ordifferent, each represents a hydrogen atom, a chlorine atom, a bromineatom, a nitro group, a methyl group, a methoxy group or an ethoxy group.

Of the above-mentioned hardening accelerator, the urea compoundsrepresented by the formula (VIII) are particularly preferred since theepoxy resin composition containing the same has sufficientpreservability and is rapidly hardenable at relatively low temperatures.Specific examples of the urea compounds of the formula (VIII) areN-(3-chloro-4-methoxyphenyl)-N',N'-dimethylurea,N-(4-chlorophenyl)-N',N'-dimethylurea,N-(3-chloro-4-ethylphenyl)-N',N'-dimethylurea,N-(3-chloro-4-methylphenyl-N',N'-dimethylurea,N-(3,4-dichlorophenyl)-N',N'-dimethylurea,N(4-ethoxyphenyl)-N',N'-dimethylurea,N-(4-methyl-3-nitrophenyl-N',N'-dimethylurea, and the like.

The epoxy resin composition according to the present inventionessentially comprises the aforesaid epoxy resin and hardener at theso-called chemical equivalent ratio. If in using the hardeningaccelerator, the hardener is desirably added in an amount lower than thechemical equivalent ratio. More specifically, the hardener is used inamounts of 40 to 90%, preferably 50 to 80%, of the chemical equivalentamounts based on the total epoxy functional group. If the amounts ofhardener is less than 40% of the chemical equivalent amounts, heatresistance of the hardened product is insufficient, and if it exceeds90% of the chemical equivalent amounts, the hardened product becomesbrittle.

The hardening accelerator is used in amounts of from 1 to 15 parts byweight per 100 parts by weight of the total amount of the epoxy resinand the additive. If the amount of the hardening accelerator is lessthan 1.5 parts by weight, reduction of the hardening temperature cannotbe achieved, and amounts exceeding 15 parts by weight decreases themolecular weight to deteriorate heat resistance. Moreover, when theadditives of the formula (I) according to the present invention containa functional group which contributes to hardening, it is desirable todecrease the amount of the hardener depending on the functionality ofsuch a functional group.

Reinforcing materials in which the epoxy resin composition isimpregnated to prepare an intermediate material for a composite includechops, yarns, tapes, sheets, knitted products, mats and paper-likeproducts made of carbon fiber.

Impregnation of the epoxy resin composition of the present inventioninto carbon fiber can be carried out by a hot-melt method or a lacquermethod, either directly or after film formation. Direct impregnation bya lacquer method is easier.

The intermediate material, the so-called prepreg, thus obtained can bemolded under appropriate conditions of pressure, temperature and time toprovide composites having extremely excellent mechanical strength.

The present invention will now be illustrated in greater detail withreference to examples and comparative examples which are given forillustrative purposes only but not for limitation.

EXAMPLES 1 to 9 AND COMPARATIVE EXAMPLES 1 TO 3

In a heating apparatus equipped with a stirrer were placed 100 g of anepoxy resin ("Epikote 828", a trade mark for a product manufactured byShell Chemicals Corp.) and 9 g of 4,4'-diaminodiphenylsulfone, and themixture was polymerized at 150° C. for 4 hours while stirring. Thereaction mixture was spouted in thin film over an ice-cooled panel tostop the polymerization to obtain Preliminary Condensate (A-1).

Additive (B) (the kind and amount are shown in Table 1 below) and 3 g ofN-(3,4-dichlorophenyl)-N',N'-dimethylurea were added to 100 g ofPreliminary Condensate (A-1), and the mixture was mixed with stirring at50° C. to obtain Resin Composition (C). Resin Composition (C) thusobtained was pasty immediately after the preparation and turned out tobe an insoluble and non-melting, transparent solid in 30 minutes at 130°C.

The pasty composition had a working life of 1 month or longer at 25° C.as determined by allowing a 50 g portion of the composition beforehardening to stand at room temperature and measuring the time at whichthe viscosity sharply increased.

Then, Resin Composition (C) was cell-casted and hardened at 130° C. for60 minutes to form a resin plate. The resulting resin plate wassubjected to bending test to obtain bending strength, modulus ofelasticity in blending and elongation, and the results obtained areshown in Table 1 below. The bending test was carried out under thecondition of L/D=16 using a sample piece of 1'×4×60 mm.

Further, 60 g of the pastry resin composition was dissolved in 40 g ofmethyl ethyl ketone to form a uniform solution. The resulting resinoussolution was impregnated into carbon fibers ("Pilofil T-1", a trade markfor a product manufactured by Mitsubishi Rayon Company Limited), and thecarbon fiber having impregnated therein the resin solution was woundaround a drum, which had previously been covered with a release papercoated with silicone, at a given width. The release paper was taken offfrom the drum and the resin-impregnated carbon fiber was dried at 70 °C. for 15 minutes to prepare a prepreg having a resin content of 40% byweight. The resulting prepreg had a gelation time of 45 minutes or moreat 140° C. as determined in accordance with JIS K-5909 and a workinglife of 1 month or more at 25° C.

The prepregs thus produced were laminated in one direction and hardenedat 130° C. for 60 minutes, and the hardened product was subjected toheat distortion temperature test and bending test. The heat distortiontemperature was determined under a load of 264 psi in parallel to thefiber axis direction in accordance with ASTM D648, and the bending testwas conducted under the condition of L/D=40 using a sample piece of2'×10×100 mm. The heat distortion temperature was 150° C. or higher ineach case, and the results of the bending test are shown in Table 1below.

In Table 1, the following compounds were used as Additive B. ##STR11##

                                      TABLE I                                     __________________________________________________________________________                   Properties of Resin Plate                                                                       Properties of Composite                                           Modulus of        Modulus of                                    Additive                                                                              Bending                                                                             Elasticity  Bending                                                                             Elasticity                                       Amount                                                                             Strength                                                                            in Bending                                                                          Elongation                                                                          Strength                                                                            in Bending                                                                          Elongation                       Run    Kind                                                                             (g)  (Kg/mm.sup.2)                                                                       (Kg/mm.sup.2)                                                                       (%)   (Kg/mm.sup.2)                                                                       (Kg/mm.sup.2)                                                                       (%)                              __________________________________________________________________________    Example 1                                                                            B-1                                                                              30   21    565   8.8   215   13.3 × 10.sup.3                                                               1.5                              Example 2                                                                            B-2                                                                              5    22    572   8.9   216   13.4 × 10.sup.3                                                               1.6                              Example 3                                                                            B-2                                                                              30   25    590   9.2   229   13.6 × 10.sup.3                                                               1.8                              Example 4                                                                            B-2                                                                              70   21    573   9.7   214   13.5 × 10.sup.3                                                               1.7                              Example 5                                                                            B-3                                                                              30   23    585   9.0   227   13.4 × 10.sup.3                                                               1.8                              Example 6                                                                            B-4                                                                              20   22    574   8.9   220   13.2 × 10.sup.3                                                               1.6                              Example 7                                                                            B-5                                                                              30   21    569   8.6   217   13.2 × 10.sup.3                                                               1.6                              Example 8                                                                            B-6                                                                              40   24    592   9.1   230   13.5 × 10.sup.3                                                               1.7                              Example 9                                                                            B-7                                                                              10   22    571   8.7   218   13.3 × 10.sup.3                                                               1.6                              Comparative                                                                          -- --   18    367   5.5   181   12.4 × 10.sup.3                                                               1.4                              Example 1                                                                     Comparative                                                                          B-3                                                                              0.5  18    381   5.7   184   12.5 × 10.sup.3                                                               1.5                              Example 2                                                                     Comparative                                                                          B-3                                                                              170  17    310   10.4  165   12.3 × 10.sup.3                                                               1.5                              Example 3                                                                     __________________________________________________________________________

EXAMPLES 10 TO 14 AND COMPARATIVE EXAMPLES 4 TO 6

In a heating apparatus equipped with a stirrer were charged 100 g ofEpikote 818 and Additive B as shown in Table 2 below, and the mixturewas uniformly mixed at 60° C. for 10 minutes with stirring. A hardenerand a hardening accelerator as shown in Table 2 were added thereto,followed by uniformly mixing at 60° C. for 10 minutes to obtain ResinComposition (E).

Resin Composition (E) was molded into a plate at 130° C. for 60 minutesby a cell-casting method, and the resulting molded product was subjectedto bending test in the same manner as in Example 1. The results obtainedare shown in Table 2 below.

Further, Resin Composition (E) was uniformly impregnated into carbonfibers, and the resin-impregnated carbon fibers were orientated in onedirection to form a sheet prepreg. The prepregs thus obtained werelaminated and hardened in a mold at 90 ° C. for 1 hour and then at 130°C. for 1 hour under a pressure of 7 Kg/cm². The hardened product wassubjected to bending test in the same manner as in the foregoingexamples, and the results obtained are shown in Table 2 below.

In Table 2, the following compounds were used as Additive B, hardenerand hardening accelerator.

    ______________________________________                                        Additive B                                                                     ##STR12##                    B-8                                              ##STR13##                    B-9                                                      Hardener                                                             H-1      4,4'-Methylenedianiline                                              H-2      Dicyandiamide                                                                 Hardening Accelerator                                                HA-1     N-(3,4-Dichlorophenyl)-N',N'-dimethylurea                            HA-2     N-(3-Chloro-4-methylphenyl)-N',N'-dimethylurea                       HA-3     N-(4-Chlorophenyl)-N',N'-dimethylurea                                HA-4     N-(2-Chlorophenyl)-N',N'-dimethylurea                                HA-5     N-(4-Ethoxyphenyl)-N',N'-dimethylurea                                ______________________________________                                    

                                      TABLE 2                                     __________________________________________________________________________                                 Properties of Resin Plate                                                                      Properties of Composite                             Hardening      Modulus of       Modulus of                    Additive                                                                              Hardener                                                                              Accelerator                                                                            Bending                                                                             Elasticity                                                                          Elonga-                                                                            Bending                                                                             Elasticity                                                                          Elonga-                    Amount  Amount   Amount                                                                             Strength                                                                            in Bending                                                                          tion Strength                                                                            in Bending                                                                          tion                Run Kind                                                                             (g)  Kind                                                                             (g)  Kind                                                                              (g)  (Kg/mm.sup.2)                                                                       (Kg/mm.sup.2)                                                                       (%)  (Kg/mm.sup.2)                                                                       (Kg/mm.sup.2)                                                                       (%)                 __________________________________________________________________________    Ex. 10                                                                            B-8                                                                              30   H-1                                                                              30   --  --   22    562   8.8  219   13.2                                                                          × 10.sup.3                                                                    1.                  Ex. 11                                                                            B-8                                                                              30   H-2                                                                              5    HA-1                                                                              5    25    581   9.3  235   13.5                                                                                1.8mes. 10.sup.3    Ex. 12                                                                            B-8                                                                              30   "  10   "   5    22    568   8.6  221   13.1                                                                                1.6mes. 10.sup.3    Ex. 13                                                                            B-8                                                                              30   "  5    "   20   21    565   8.7  225   13.3                                                                                1.imes. 10.sup.3    Ex. 14                                                                            B-9                                                                              30   "  5    HA-2                                                                              5    23    560   8.7  216   13.2                                                                                1.6mes. 10.sup.3    Comp.                                                                             -- --   "  5    HA-1                                                                              5    13    291   7.6  184   12.4                                                                                1.3mes. 10.sup.3    Ex. 4                                                                         Comp.                                                                             B-12                                                                              1   "  5    HA-2                                                                              5    13    295   7.5  183   12.5                                                                                1.4mes. 10.sup.3    Ex. 5                                                                         Comp.                                                                             B-12                                                                             160  "  5    "   5     8    215   12.3 175   12.3                                                                                1.4mes. 10.sup.3    Ex. 6                                                                         __________________________________________________________________________

EXAMPLES 15 TO 31

A mixture of piperidine (85 g) and allyl glycidyl ether (107 g) wasreacted at 150° C. for 3 hours while stirring. After completion ofreaction, formation of Compound B-10 was confirmed by NMR spectralanalysis. ##STR14##

In analogous manners, starting compounds (V), (VI) or (VII), and (IV)were mixed in a weight ratio shown in Table 3 and the mixture wasreacted to obtain Compound B-11 to B-22.

The procedures of Example 1 were repeated except that the additivesshown in Table 3 and the hardeners and the hardening accelerators shownin Table 4 were used to prepare resin plates and carbon fibercomposites. The mechanical properties of these samples were determinedin the same manner as in Example 1. The results obtained are shown inTable 4 below.

                  TABLE 3                                                         ______________________________________                                        Starting Compounds                                                                   (V) or        Amount           Amount                                  Additive                                                                             (VI) or (VII) (g)      (IV)    (g)                                     ______________________________________                                        B-11   Dibenzylamine 197      Dipentene                                                                             152                                                                   Monoxide                                        B-12   Piperidine     85      Butyl   131                                                                   Glycidyl                                                                      Ether                                           B-13   p-Aminobenzoic                                                                              137      Limonene                                                                              168                                            Acid                   Dioxide                                         B-14   N-Methyl-      59      Ethylene                                                                              175                                            formamide              Glycol                                                                        Diglycidyl                                                                    Ether                                           B-15   4-Hydroxy-    151      Vinylcyclo-                                                                           140                                            acetanilide            hexene                                                                        Dioxide                                         B-16   Acetanilide   135      Phenyl  150                                                                   Glycidyl                                                                      Ether                                           B-17   N,N-Dimethylurea                                                                             88      Epichloro-                                                                              56.5                                                                hydrin                                          B-18   N,N'-Diallylurea                                                                            140      Dimethyl-                                                                             168                                                                   pentane                                                                       Dioxide                                         B-19   N,N'-Di-n-    172      Butadiene                                                                              70                                            butylurea              Oxide                                           B-20   N,N'-Dibenzylurea                                                                           240      Divinyl-                                                                              162                                                                   benzene                                                                       Dioxide                                         B-21   Acetanilide   177      Vinylcyclo-                                                                           140                                                                   hexene                                                                        Dioxide                                         B-22   N,N'-Diethyl- 120      Limonene                                                                              168                                            thiourea               Dioxide                                         ______________________________________                                        Ad-                                                                           di-                                                                           tive Chemical Structure                                                       ______________________________________                                        B-11                                                                                ##STR15##                                                               B-12                                                                                ##STR16##                                                               B-13                                                                                ##STR17##                                                               B-14                                                                                ##STR18##                                                               B-15                                                                                ##STR19##                                                               B-16                                                                                ##STR20##                                                               B-17                                                                                ##STR21##                                                               B-18                                                                                ##STR22##                                                               B-19                                                                                ##STR23##                                                               B-20                                                                                ##STR24##                                                               B-21                                                                                ##STR25##                                                               B-22                                                                                ##STR26##                                                               ______________________________________                                    

                                      TABLE 4                                     __________________________________________________________________________                                 Properties of Resin Plate                                                                      Properties of Composite                             Hardening      Modulus of       Modulus of                    Additive                                                                              Hardener                                                                              Accelerator                                                                            Bending                                                                             Elasticity                                                                          Elonga-                                                                            Bending                                                                             Elasticity                                                                          Elonga-                    Amount  Amount   Amount                                                                             Strength                                                                            in Bending                                                                          tion Strength                                                                            in Bending                                                                          tion                Run Kind                                                                             (g)  Kind                                                                             (g)  Kind                                                                              (g)  (Kg/mm.sup.2)                                                                       (Kg/mm.sup.2)                                                                       (%)  (Kg/mm.sup.2)                                                                       (Kg/mm.sup.2)                                                                       (%)                 __________________________________________________________________________    Ex. 15                                                                            B-11                                                                             30   H-2                                                                              3    HA-3                                                                              5    26    591   9.3  219   13.8                                                                          × 10.sup.3                                                                    1.8                 Ex. 16                                                                            B-12                                                                             40   "  5    HA-1                                                                              2    27    590   9.4  220   13.9                                                                                1.8mes. 10.sup.3    Ex. 17                                                                            "  40   "  5    "   9    25    582   9.1  218   13.6                                                                                1.9mes. 10.sup.3    Ex. 18                                                                            B-13                                                                             40   "  5    HA-4                                                                              3    24    585   9.0  225   13.7                                                                                1.8mes. 10.sup.3    Ex. 19                                                                            "  40   "  5    "   9    26    588   9.2  219   13.8                                                                                1.8mes. 10.sup.3    Ex. 20                                                                            B-14                                                                             30   "  5    HA-1                                                                              3    25    584   9.3  227   13.8                                                                                1.7mes. 10.sup.3    Ex. 21                                                                            B-15                                                                             30   "  3    HA-3                                                                              5    27    593   9.6  225   13.9                                                                                1.8mes. 10.sup.3    Ex. 22                                                                            B-7                                                                              40   "  5    HA-1                                                                              2    28    592   9.4  225   14.0                                                                                1.9mes. 10.sup.3    Ex. 23                                                                            "  "    "  "    "   9    25    583   9.0  216   13.5                                                                                1.9mes. 10.sup.3    Ex. 24                                                                            B-16                                                                             40   "  5    HA-4                                                                              3    25    586   9.0  226   13.8                                                                                1.8mes. 10.sup.3    Ex. 25                                                                            "  "    "  "    "   9    27    590   9.3  226   13.9                                                                                1.9mes. 10.sup.3    Ex. 26                                                                            B-17                                                                             30   H-2                                                                              5    HA-1                                                                              3    24    581   9.1  223   13.5                                                                                1.8mes. 10.sup.3    Ex. 27                                                                            B-18                                                                             30   H-2                                                                              3    HA-3                                                                              5    26    590   9.4  224   14.0                                                                                1.9mes. 10.sup.3    Ex. 28                                                                            B-19                                                                             40   H-2                                                                              5    HA-1                                                                              2    25    588   9.4  219   13.9                                                                                1.9mes. 10.sup.3    Ex. 29                                                                            "  "    "  "    HA-1                                                                              9    26    585   9.3  230   13.5                                                                                1.9mes. 10.sup.3    Ex. 30                                                                            B-20                                                                             40   "  "    HA-4                                                                              3    24    590   9.0  226   13.8                                                                                1.7mes. 10.sup.3    Ex. 31                                                                            "  "    "  "    "   9    28    591   9.3  219   13.8                                                                                1.8mes. 10.sup.3    __________________________________________________________________________

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to those skilled inthe art that various changes and modifications can be made thereinwithout departing from the spirit and scope thereof.

What is claimed is:
 1. An intermediate for a composite material, whichintermediate comprises carbon fibers impregnated with an epoxy resincomposition containing epoxy resin and at least one of compoundsrepresented by formula (I): ##STR27## wherein R₁ and R₂, which may bethe same or different, each represents .Iadd.a hydrogen atom or.Iaddend.a substituted or unsubstituted, saturated alicyclic grouphaving 5 to 17 carbon atoms, a substituted or unsubstituted aromaticgroup having 6 to 17 carbon atoms, or a substituted or unsubstituted,saturated or unsaturated 5- or 6-membered heterocyclic group containingN, O or S as hetero atoms or a group of formula ##STR28## wherein R₅ andR₆, which may be the same or different, each represents a hydrogen atomor a substituted or unsubstituted, saturated aliphatic group having 1 to17 carbon atoms, a substituted or unsubstituted, saturated alicyclicgroup having 5 to 17 carbon atoms, an aromatic group having 6 to 17carbon atoms, or a substituted or unsubstituted, saturated 5- or6-membered heterocyclic group containing N, O or S as heteroatoms.Iadd., provided that not more than one of R₁ and R₂ are hydrogen,and provided that R₁ and R₂ may combine to form an aromaticring.Iaddend.;R₃ and R₄, which may be the same or different, each hasthe same meaning as defined for R₁ and R₂, or a group of the formulaR--OCH₂ -- wherein R has the same meaning as defined for R₁ and R₂except that R is not a hydrogen atom; and X represents an oxygen atom, asulfur atom or N-R₇ wherein R₇ .[.represents a hydrogen atom or.]. hasthe same meaning as defined for R₁ and R₂.
 2. An intermediate as inclaim 1, wherein the substituent for the substituted aliphatic,alicyclic, aromatic or heterocyclic group as represented by R₁, R₂, R₅,R₆ or R₇ is a halogen atom, an alkoxy group having 1 to 3 carbon atoms,an aryloxy group having 6 to 17 carbon atoms or an acyl group having 2to 7 carbon atoms.
 3. An intermediate as in claim 1, wherein R₂ containsa substituted or unsubstituted aromatic group.
 4. An intermediate as inclaim 1, wherein at least one of R₃ and R₄ contains a substituted orunsubstituted, saturated alicyclic or aromatic group.
 5. An intermediateas in claim 1, wherein the compound or compounds is or are present in anamount of from 2 to 150 parts by weight per 100 parts by weight of thetotal amounts of the epoxy resin composition.
 6. An intermediate as inclaim 5, wherein the compound or compounds is or are present in anamount of from 10 to 50 parts by weight per 100 parts by weight of thetotal amounts of the epoxy resin composition.
 7. An intermediate as inclaim 1, wherein the resin composition further contains a hardener, ahardening accelerator, or both.
 8. An intermediate as in claim 7,wherein the hardener is present in an amount of from 40 to 90% of thechemical equivalent amounts based on the total epoxy functional group.9. An intermediate as in claim 8, wherein the hardener is present in anamount of from 50 to 80% of the chemical equivalent amounts based on thetotal epoxy functional group.
 10. An intermediate as in claim 7, whereinthe hardener is dicyandiamide.
 11. An intermediate as in claim 7,wherein the hardener accelerator is present in an amount of from 1.5 to15 parts by weight per 100 parts by weight of the total amounts of theepoxy resin and the additives.
 12. An intermediate as in claim 11,wherein the hardening accelerator is present in an amount of from 2 to10 parts by weight per 100 parts by weight of the total amounts of theepoxy resin and the additives.
 13. An intermediate as in claim 7,wherein the hardening accelerator is a compound represented by .[.the.].formula .[.(I).]. .Iadd.(II).Iaddend.: ##STR29## wherein Y and Z, whichmay be the same or different, each represents a hydrogen atom, achlorine atom, a bromine atom, a nitro group, a methyl group, a methoxygroup or an ethoxy group.
 14. An intermediate as in claim 1, wherein theepoxy resin composition comprises at least one preliminary condensatewhich is obtained by subjecting at least one polyamine or acidicsubstance having a polycarboxylic group, a polycarboxylic acid anhydridegroup or a mixed group thereof and an epoxy resin having at least oneepoxy group at a chemical equivalent ratio of from 1:1 to 1:6 to heattreatment at a temperature of from 50° to 200° C. to increase theviscosity of the mixture at least 3 times without inducing gelatin. 15.An intermediate as in claim 14, wherein the chemical equivalent ratio isfrom 1:1.4 to 1:6.
 16. An intermediate as in claim 15, wherein thechemical equivalent ratio is from 1:1.5 to 1:5.
 17. An intermediate asin claim 14, wherein the epoxy resin is bisphenol A diglycidyl ether.18. An intermediate as in claim 14, wherein the polyamine is4,4'-diaminodiphenylsulfone.
 19. An intermediate for a compositematerial, which intermediate comprises a carbon fiber impregnated withan epoxy resin composition containing at least one compound representedby .[.the.]. formula (I): ##STR30## wherein R₁ and R₂, .Iadd.which maybe the same or different, .Iaddend.each represents a substituted orunsubstituted, saturated alicyclic group having 5 to 17 carbon atoms, asubstituted or unsubstituted aromatic group having 6 to 17 carbon atoms,or a substituted or unsubstituted, saturated or unsaturated 5- or6-membered heterocyclic group containing N, O or S as hetero atoms.Iadd.or a group of formula ##STR31## wherein R₅ and R₆, which may bethe same or different, each represents a hydrogen atom or a substitutedor unsubstituted saturated aliphatic group having 1 to 17 carbon atoms,a substituted or unsubstituted, saturated alicyclic group having 5 to 17carbon atoms, an aromatic group having 6 to 17 carbon atoms, or asubstituted or unsubstituted, saturated 5- or 6-membered heterocyclicgroup containing N, O or S as hetero atoms, provided that R₁ and R₂ maycombine to form an aromatic ring.Iaddend.;R₃ and R₄, which may be thesame or different, each has the same meaning as defined for R₁ and R₂,or a group of the formula R--OCH₂ -- wherein R has the same meaning asdefined for R₁ and R₂ ; and X represents an oxygen atom, a sulfur atomor .[.N--R₆ .]. .Iadd.N--R₇ .Iaddend.wherein .[.R₆ represents a hydrogenatom or.]. .Iadd.R₇ .Iaddend.has the same meaning as defined for R₁ andR₂, R₁, R₂, R₃ and R₄ thus represent a bulky and highly rigidsubstituent.